“I got a phone call from her camp to tell me that she would very much like for me to be a representative of my age group in the new fashion campaign,” McDonald tells The Telegraph. “I was of course delighted and said yes.”

Beyoncé describes McDonald, who has taught dance for over 40 years and still teaches and takes classes every day, as an inspiration, and McDonald believes that the star felt it was important to reach new audiences with her clothing line, which had previously been targeted at younger fashion fans with campaigns fronted by models like 18 year-old Selah Marley.

Karen in the new Ivy Park campaign

“I think that fashion is a part of her art and she realised how important it is to reach all age groups within this era of female empowerment,” McDonald says. “When you see someone who is very powerful extending themselves, you feel inclined to [want to] be a part of that.”

Working out so regularly, McDonald acknowledges, is not a priority for everyone in their sixties, but she says that getting the right kit can help anyone to start making a confident effort. Indeed, when the singer launched Ivy Park back in March 2016, she did so with the intention of encouraging women all over the world, of all ages, to exercise more and to look and feel great while doing so.

“Of course I want to wear different things when I exercise now to when I was 20,” she considers. “I like things that are trendy, but also classic. Sometimes I want to wear baggy clothes, but most days I like sleek ones that show my lines. I like things that show my body off, because dancers work hard to keep in shape.”

McDonald has worked with Beyoncé for several years now, including on performances for the Grammys, around her hit album Lemonade and on television commercials. She had previously worked with Michael Jackson on his Thriller video, as well as extensively on Broadway, which she describes as a real passion.

“They all have one thing in common; a sense of discipline and greatness for their art,” she says of what the performers she has worked with are like in real life.

“Beyoncé is a force. She’s energetic, so powerful, when she walks into the room it’s like she expands as she’s walking towards you.

"She’s the best, and she wants everyone around her to give their best. I love Beyoncé because she’s studied all styles of dance and she’s really worked hard. Is her talent natural? Absolutely it is, but you have to have that work ethic to be truly that great. As soon as you think you know who she is, she shakes it up and comes out with something completely different, and that takes real work.”

Laverne Cox models Ivy Park activewear

As for Beyoncé’s own workout style, McDonald doesn’t exactly dispel the rumours that the icon (slash bionic woman) can dance all day in heels pain-free.

“It depends on what day it is,” she says carefully. “She’s the kind of person who gets down dirty when she works out, so it depends what type of rehearsal it is and how long it lasts. She does have a look, and expresses her own sense of style when she's exercising.

"But in a six hour dance rehearsal you might start in trainers and then work it up to translate into heels and gowns and sequins as the practices go on, to reflect what you might actually do in the performance.”

In Ivy Park, it seems, both dancer and choreographer have found something practical and personal to wear and feel great in.

“I always like to be fashionable, even at a dance class, it’s just a part of the dance culture,” McDonald says. “A lot of things that dancers have worn over the years, designers have copied and brought them into the fashion world because dancers have always had a good sense of style.